@twangy57
A few years ago I welcomed a PrimaLuna EVO 100 Tube Preamplifier to my rig and ended up with a similar situation that you have - a pairing issue. Voicing was slightly veiled on some tracks, and generally speaking, most tracks had the lead singer in the background, rather than forward - or upfront.
Like your McInstosh, the PrimaLuna required that the amplifier's input impedance be at least 10 times higher than the preamp's output impedance. And like your McIntosh, the PrimaLuna was 10K...so 100K was where my amp needed to be.
As it was at the time, I was using an NAD C275BEE. This amp had both fixed and variable inputs. In the fixed mode, the impedence was 10K, while the variable input (full) was 100K.
I would love to tell you that as soon as I switched to full variable input everything changed for the better, but it did not. While it certainly increased the quality of the sound, it was not where I knew it should be. Still had some issues with vocals and bass was good but a little muddy.
I believed at the time- and still do- that the issue was the dampening factor. DF measures the amplifier's ability to control a speaker's movement after a signal stops. DF is calculated as: Speaker Impedance / (Amplifier Output Impedance + Cable Resistance).
The NAD c275BEE DF vs. frequency is typical of most solid-state power amplifiers: high at low frequencies, then declining throughout the audioband. Hence, the sound was bettered as the volume was turned up. The lower the output impedance of the amplifier, the higher the DF, so this is what you would have been experiencing with the Adcom.
Also, adding speaker cable resistance will lower the DF, so while I am not wanting to get into a cable conversation, it's important to use good quality, low-resistance cables. I don't think my AudioQuest 5 cable was causing the issue or adding to it, but it is possible that your cables may be compounding the problem for you. Don't rule out a chain reaction.
That is a lot to digest. And it is at those times when it is best to try not to fight the power, but to simply start over. I sold the PrimaLuna, upgraded my amplifier and even changed out speakers, cable, etc. I succeeded in getting the sound I craved by ditching a bad partnership that started by simply using what gear I could afford in hopes of hitting pay dirt. I was merely hoping to get lucky.
I am not so young either, so it is best to get to the point of bliss sooner, rather than later. Save time; do not waste it on poor pairings.
I think it was the Pass Labs CEO who states that building a system starts with buying the best speakers you can afford. I guess you have done that with the Dynaudio's, so work backwards from there as you seem to be doing. Keep the DAC. Get a good phono Preamp to go with the Rega (a $400 Rega MM or MC phono preamp will sound much better than your preamp in the McIntosh). Use good cables (Rega sells a $150 low cap TT cable to go between preamp and table). But the guts of your system - your amp/preamp pairing that serves the speakers the best is paramount. Good luck.
